Betting on Ben S. Bernanke has been the most profitable trade for government bond investors in 16 years, defying lawmakers in the U.S. and abroad who said the Federal Reserve chairman’s policies would lead to runaway inflation and the dollar’s debasement.

Treasuries due in 10 or more years have returned 28 percent in 2011, exceeding the 24.4 percent gain in all of 2008 during worst financial crisis since the Great Depression, according to Bank of America Merrill Lynch indexes. Not since 1995, when the securities soared 30.7 percent, have investors done so well owning longer-dated U.S. government debt.

Rather than collapsing, the dollar has risen 2.6 percent to 78.501 against the currencies of six major U.S. trading partners including the euro and yen, since the Fed announced QE2 in November, based on IntercontinentalExchange Inc.’s Dollar Index.

“I’m not sure the Republicans’ grasp of the Fed and everything that goes with it is particularly strong,” said David Ader, head of U.S. government bond strategy at CRT Capital Group LLC in Stamford, Connecticut, in a Sept. 22 telephone interview. “The data confirms the Fed’s concerns. If there’s uncertainty and a lack of confidence, the focal point is not at the Federal Reserve, but much more in the hands of the people that wrote this letter.”